Observation and characterization of new FIR laser lines from formic acid

FTIR spectra of the ν6 and ν8 bands of 13C formic acid molecule—Assignment of FIR-laser lines

“…The obtained results enabled us to check the assignments of FIR laser emissions observed in [2][3][4] and also to assign new laser transitions. The action of the optically pumped laser is based on the creation of a population between rotational levels in the excited vibrational state when pumping IR transition between ground and excited In Tables 3 and 4 the letters in column ''Note" mean the following: ''c"-confirmation of the previous assignment, ''r"-reassignment, ''f"-assignment for the first time.…”

“…Table 3 represents data from [2] while Table 4 is concerned with measurements from Refs. [3,4]. In both tables the column ''Note" indicates what laser transition was previously assigned and confirmed, here indicated by letter ''c".…”

“…a Only one component of rotational doublet is given. [2][3][4]. The assignments were made by comparing the calculated and observed frequencies of the pumped and emitted transitions together with additional requirement that both transitions possess a common upper level.…”

“…Also it should be noted that in Refs. [3,4] an offset of the IR absorption relative to the center frequency of the pump were determined. Measured offset values together with calculated ones are shown in Table 4.…”

“…They measured the frequencies of laser lines with an accuracy of about 1 MHz and gave tentative assignment almost for all transitions. In the second work published in 1998 [3] Luis et al could observe five new far-infrared lines using a more widely tuned waveguide CO 2 laser. The authors measured the wavelengths of the laser lines with an uncertainty of about ±0.5 lm and also the offset absorption frequencies.…”